This invention relates to a holding apparatus for a work to be coated such as a bumper for an automobile while rotating the same.
In order to provide high grade feeling to an automobile, a degree of coating of a body of the automobile is a very important factor, and various coating techniques have been developed to increase high grade feeling together with improvement in efficiency of coating by individual automobile makers. Also for a bumper, a collapsible urethane bumper is employed in place of a conventional bumper made of sheet metal, and coating is applied to such urethane bumper to increase the high grade feeling of the automobile. A coating process of the urethane bumper generally includes a washing step, a masking step, an undercoating and drying step, and a final coating and drying step.
In order to maintain a quality of coating, it is important to minimize causes of failure in coating. One of causes of failure in coating is a sagging of paint which takes place when a vertical face or an inclined face of a work is coated. As one of causes of such sagging, the thickness of a film of paint is excessively great or the viscosity of paint is excessively low, and if part of paint flows down over several millimeters, then the film of the paint will be swollen and form a sagging mark at a location at which such flow of the paint stops. As countermeasures for preventing the sagging of paint, various methods may be available including, for example, to decrease the thickness of a film of paint, to increase the viscosity of paint and to accelerate drying of paint. Also rotating a work for a predetermined period of time immediately after coating of the work is an effective method for preventing the sagging of paint.
For example, U.S. Pat. No. 4,874,639 discloses, under the title of coating method and apparatus on a coating line, a technique of rotating a body of an automobile while transporting the automobile body by means of a transport truck to dry coated paint on the automobile body. The coating method and apparatus disclosed in the patent, however, is suitably applied to a large size work such as a body of an automobile and is great in size and complicated in construction. Accordingly, it is difficult to apply the coating method and apparatus to coating of an elongated work such as a bumper or an air spoiler.